Effect of Bed Length and Vapor Maldistribution on Structured Packing Performance

Recent tests of a 250 m/m structured packing in a 1.22 m diameter column have produced some unanticipated results. Using two quite different systems, mass transfer performance in a relatively short 1.69 m bed was significantly better than previous results in a longer 3.78 m bed. No bed length effect was found on pressure drop. Two different severe vapor maldistributions were studied using a vacuum system with the 1.69 m bed. No significant effect of vapor maldistribution on mass transfer efficiency, capacity and pressure drop was observed. The HETP “hump”, or deterioration of mass transfer performance, previously reported in a 3.78 m bed was again found in the short bed using 11.4 bar butane. However, tests with a 133 m/m packing did not show the hump in a 3.81 m bed. The experimental results are compared to predictions from various literature models.